Given the code fragments:

class Caller implements Callable {

String str;

public Caller (String s) {this.str=s;}

public String call()throws Exception { return str.concat ("Caller");}

}

class Runner implements Runnable {

String str;

public Runner (String s) {this.str=s;}

public void run () { System.out.println (str.concat ("Runner"));}

}

and

public static void main (String[] args) throws InterruptedException, ExecutionException {

ExecutorService es = Executors.newFixedThreadPool(2);

Future f1 = es.submit (new Caller ("Call"));

Future f2 = es.submit (new Runner ("Run"));

String str1 = (String) f1.get();

String str2 = (String) f2.get(); //line n1

System.out.println(str1+ ":" + str2);

es.shutdown();

}

What is the result?